Henry Bain

The effect of cultivar, maturity and storage on photo-induced changes in the total glycoalkaloid and chlorophyll contents of potatoes (Solanum tuberosum)

Abstract The tubers of 20 potato genotypes were exposed to light, equivalent to a radiant flux density of 140 μmol−1 s−1 m−2, approximating to dull daylight conditions, for a continous period of 48 h. Tubers were exposed when immature, mature and also after a period of storage. There were significant differences between the genotypes in their rates of increase of both glycoalkaloid and chlorophyll contents. Notably, potato genotypes responded differently to light in their rates of glycoalkaloid and chlorophyll synthesis, this being dependent on the physiological state of the tubers as well as their inherent characteristics.

Evaluation of liquid chromatography–atmospheric pressure chemical ionisation–mass spectrometry for the identification and quantification of desulphoglucosinolates

The use of liquid chromatography–atmospheric pressure chemical ionisation–mass spectrometry has been investigated as a potential method for both the identification and quantification of desulphoglucosinolates. The results indicate that this methodology is particularly useful as a rapid technique for the confirmation of the identity of desulphoglucosinolates and has, in full scan mode, limits of detection at least an order of magnitude lower than is normally achieved by conventional high pressure liquid chromatography with UV detection. It has been demonstrated that, using a per-deuterated desulphoglucosinolate as an internal standard, quantification could be achieved, but for accurate analysis at low concentrations it would be necessary to produce independent calibration curves for each desulphoglucosinolate present in the sample. Copyright

The Effect of Low-Temperature Storage on the Glycoalkaloid Content of Potato (Solanum tuberosum) Tubers

Tubers from six cultivars selected on the basis of their rates of glycoalkaloid accumulation in response to light exposure were stored at 10, 7 and 4°C. After 9 weeks at 10°C a subset from each cultivar was removed and subsequently stored at lower temperatures. Samples were removed after 9, 18 and 24 weeks storage and analysed for their glycoalkaloid content. At all temperatures the rate of glycoalkaloid accumulation was independent of the level found at harvest and significant interactions were found between cultivar and temperature. The highest rates of accumulation were seen in tubers from the cultivars Brodick and Pentland Crown stored at 4°C. During the first 9 weeks of storage at this temperature the glycoalkaloid content of these two cultivars increased by 7·4 and 19·1 mg per 100 g fresh weight respectively and thereafter remained constant. At 7°C glycoalkaloid content tended to increase more rapidly than at 10°C with again the greatest increases being found for Brodick and Pentland Crown. In the case of the former glycoalkaloid content increased linearly during the 24 weeks of the experiment but the glycoalkaloid content of Pentland Crown tubers stored at 7°C increased rapidly in the first 9 weeks and thereafter increased more slowly, reaching a final value which exceeded the recommended maximum glycoalkaloid concentration for human consumption by 50%. Cultivars which did not accumulate glycoalkaloids rapidly in response to light exposure were the most stable and least sensitive to storage temperature. Tubers transferred to colder conditions nine weeks after storage at 10°C did not accumulate glycoalkaloids at a similar rate to those placed in similar conditions soon after harvest.

Effect of bruising on the total glycoalkaloid and chlorogenic acid content of potato (Solanum tuberosum) tubers of five cultivars

Tubers from five potato cultivars were selected on the basis of their low, intermediate or high rates of glycoalkaloid synthesis in response to stresses such as light or cold storage temperatures. The tubers were subjected to a standard degree of damage sufficient to cause bruising but not severe damage such as cracking or splitting. Increases in glycoalkaloid levels in response to damage were observed in all cultivars. Importantly, the rates of glycoalkaloid synthesis in response to damage were in good agreement with cultivar response to light and cold temperature stress. The cultivars, Ailsa and Eden, exhibited a slower response than the higher synthesis rates observed in Pentland Dell or Brodick. The cultivar Torridon exhibited severe internal damage symptoms throughout the tuber as opposed to localised bruising observed in the other cultivars. The extensive cell death observed in the tubers of the cultivar Torridon severely curtailed glycoalkaloid and chlorogenic acid synthesis. The increased levels of glycoalkaloids in response to bruising damage ranged from approximately 27% (Ailsa, Torridon) to 130% for the cultivar Brodick. Chlorogenic acid levels increased in two cultivars (Brodick and Torridon) but not in the others, Ailsa, Eden and Pentland Dell. The α-chaconine/α-solanine ratios observed within the five cultivars were in good agreement with previous research. The consistency across years is notable, indicating a strong relationship in the synthesis of the two glycoalkaloids. The results are discussed in terms of implications for the potato industry, for the retail trade and also for selection within potato breeding programmes.

The Development and Evaluation of Capillary Electrophoretic Methods for the Determination of the Major Phenolic Constituents of Potato (Solanum tuberosum) Tubers

A range of capillary electrophoretic methods utilizing both capillary zone (CZE) and micellar electrokinetic techniques were developed for the separation of 15 compounds consisting of a complex micture of coumarins, cinnamic and phenolic acids. Factors influencing their migration times are evaluated and discussed, and conditions optimized for their quantitative analyses. These techniques were applied to potato extracts, in which chlorogenic acid and caffeic acids were identified and simultaneously quantified. A CZE method was also developed for the separation of chlorogenic acid isomers. These techniques were utilized in a preliminary study to evaluate the effect of light on both the isomeric ratios and total chlorogenic acid content of potato tubers. The results indicated that prolonged exposure to light resulted not only in an increase in total chlorogenic acid content but also in a significant change in the relative proportions of the two major chlorogenic isomers present in the tubers.

The effect of gamma irradiation on glycoalkaloid and chlorophyll synthesis in seven potato cultivars

The use of gamma irradiation to control sprouting and increase the length of storage time of potatoes has been proposed as an alternative to cold storage or the use of chemical sprout suppressants. Indeed, it is applied on a commercial-scale to potatoes in Japan. This research reports on the effects of different levels of gamma irradiation on seven potato cultivars in relation to chlorophyll and glycoalkaloid synthesis on subsequent exposure to light after a period of storage. There were significant genotype differences between cultivars in their response to gamma irradiation, with some cultivars exhibiting dramatically reduced levels of glycoalkaloid synthesis compared with others. Also, cultivars responded differently to variable irradiation levels. The implications of the results are discussed in relation to public health concerns and selection within potato breeding programmes.

Effects of Tuber-borne M-type Strain of Tobacco Rattle Virus on yield and Quality Attributes of Potato Tubers of the Cultivar Wilja

It was previously thought that Tobacco Rattle Virus (TRV) was self-eliminating from seed potato stocks and that the principal effects of the virus were the spraing symptoms (arcs or lines of corky brown tissue) formed in the tuber flesh. Recent work has clearly demonstrated that the virus can become fully and systemically established in some potato cultivars, with few, if any, tuber flesh symptoms. The studies reported here demonstrate that, in at least one such cultivar, an M-type strain of the virus can have a considerable effect on the growth and quality of the plant and its produce. When infected material was compared with healthy material, overall yield and yield components were severely affected by TRV, as were quality traits such as dry matter, after-cooking blackening and chemical components such as sugars, glycoalkaloids and chlorogenic acid. The results are discussed in terms of plant response to virus infection and plant protection mechanisms.

The evaluation of capillary zone and micellar electrokinetic capillary chromatographic techniques for the simultaneous determination of flavonoids, cinnamic and phenolic acids in blackcurrant (Ribes nigrum) bud extracts

A range of capillary electrophoretic methods utilizing both capillary zone and micellar electrokinetic techniques were evaluated for the simultaneous separation of 15 compbunds consisting of a complex mixture of flavonoids, cinnamic acids and simple phenolic acids. Factors influencing their migration times are evaluated and discussed, and conditions optimised for their quantitative analysis. These techniques were applied to crude methanolic blackcurrant bud extracts in which 11 compounds were directly identified and simultaneously quantified.